The remarkable importance of a piston as essential part of internal combustion engines is well known in the art. In such engines, the combustion process of a fuel, such as gasoline or diesel, is used in combination with an oxidizer in order to generate power. The prior function of the piston is the transferring of energy produced by the combustion process into the rotational motion of the crankshaft, thus facilitating the inter conversion of the chemical energy into mechanical energy. Said energy transferring requires the translational motion of the piston through the cylinder's walls under extremes pressure, stress and temperatures conditions. Therefore, in order to function properly, the piston must maintain the expanded gases produced in the combustion chamber isolated from the crankshaft area, must move at a high speed through the walls of the cylinder, and must be able to transmit the motion from the connecting rod to the crankshaft and to disperse the heat produced in the process in an efficient manner. Said processes require a proper lubrication, particularly between the internal cylinder walls and the piston external surface, which is fundamental in order to increase the maintenance and high performance of the engine. The oil or lubricant assists the piston's performance by decreasing the power required to reduce friction, thus reducing the wear. Similarly, the lubricant also serves as a cooling agent of the piston by carrying away heat front the piston to the oil pan and also works as a dirt removal since it removes unwanted particulates such as carbon. Additionally, other advantages of the proper lubrication are the formation of a sealing interface between the piston rings and the cylinder walls that prevents loss of compression; cushioning of the parts against vibration and impacts; noise reduction and protection against corrosion.
The prior art discloses several examples, wherein particular apertures, openings or grooves on the surface of the piston's skirt are present as alternatives or solutions to increases said lubrication. For instant, U.S. Pat. No. 4,903,580 to Bruni discloses a piston having a series of elongated notches or grooves, located at both skirt surfaces and parallel to one another. Said grooves have an angular extension of 40 degrees since they are extended approximately 40 degrees centered about a lines perpendicular to the piston pin axis and a radial depth in a range of 0.005 to 0.05 mm. The interior side of such grooves is apparently straight, without any inclination or angle. The elongated geometry and the relative position of said grooves—parallel to each other and positioned along the surface of the skirt—present a potential weakness to the structural strength of the piston. Similarly, U.S. Pat. No. 7,415,961 to Chen et al. discloses a piston having different apertures or openings called reservoirs and channels, in diverse the forms of holes, grooves and indentions. Said diverse grooves or indentions have different shapes, depths and sizes and are located on the surface of the piston skirts in an irregular manner, without following a predetermined pattern, and without being limited to a particular section of the skirt or by even any particular quantity. Circular holes, elongated grooves of different sizes and design, cross sectional or I-shaped grooves may be present alone or in combination; giving place to multiple arrangements of possible combinations, thus without considering the potential effects on the particular characteristics of the piston such as strength of the resulting piston's structure.
The prior art however, does not discloses or suggests a piston having a series of conical holes at the piston skirt, horizontally positioned with regard to the piston pin axis and located substantially at the center of each skirt section; wherein each conical hole is aligned with a drain oil hole located at the piston crown and wherein the lubrication of the piston walls is increased by the lubrication flow formed by the coordination of the particular place of said conical openings, its alignment with the oil drain holes and the oil being squirted by the rod bearing.